It was necessary to study the bonding mechanism of poly(D,L-lactide) (PDLLA) and hydroxyapatite (HA) nanoparticles because of their increasing application in medical fields. In this paper, hydrogen bonding between PDLLA and HA in PDLLA/HA nanocomposites was first investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Structural morphology and glass transition temperature (T g ) of the nanocomposites showed that there was a close interaction between polymer matrix and inorganic nanoparticls. The results from FTIR and XPS indicated that the hydrogen bonding between the CdO in PDLLA and the surface PsOH groups of HA nanocrystalline was formed indeed. Shape memory properties were improved, which further implied the existence of hydrogen bonding in these nanocomposites. Thus, we designed a schematic model of the hydrogen bonding on the base of the experimental results. It can clearly explain the interaction mechanism of polymeric phases and inorganic phase in nanocomposites.

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healthcare applications. However, the structures of OTFTs are relatively complex, which makes their fabrication process rigid and costly. Therefore, there is still enduring enthusiasm to develop new wearable pressure sensors to enhance their merits, such as high sensitivity, wide operation range, flexibility, economic fabrication, and deployment costs. [7c] Several mechanisms have been used to fabricate pressure sensors, such as piezoelectricity, [3a,10] capacitance, [1b,f,11] triboelectricity, [12] and piezoresistivity. [1c,e,13] Among them, piezoresistivity-type pressure sensors have the advantages of simple structure, low-cost, and convenient read-out, and thus have been drawn incredible attention to the development of flexible devices. To sustain large deformation, this type of flexible pressure sensor is commonly fabricated by elastic polymer materials, such as polydimethylsiloxane (PDMS), [1c,13a] polyurethane (PU), [1h] and even polypyrrole (PPy). [1d] Although such devices have shown their impressive performances, the sensitivities of those sensors are still not very high and/or their operation ranges are not wide enough for many applications. [8b] For example, the pressure sensor fabricated by Park et al. [1e] using Au-coated PDMS as the active matrix has a sensitivity of 2 kPa −1 under a pressure lower than 220 Pa. When the pressure increases above 220 Pa, its sensitivity starts to drop, and it will eventually reach saturation when the pressure reaches 3.5 kPa. Based on quantum tunneling effect, Lee et al. [1h] demonstrated a pressure sensor using a PU matrix mixed with sea-urchin shaped metal nanoparticles, and improved the sensitivity to 2.46 kPa −1 . However, its high sensitivity can be achieved only when the pressure is lower than 1 kPa. It will decrease to 0.055 kPa −1 when the applied pressure is above 10 kPa.One of the promising solutions to this issue is to adopt elastic hydrogels, which have significantly lower modulus of elasticity, for flexible pressure sensing applications. Using hollow-sphere microstructured PPy hydrogel, Bao and co-workers [1d] achieved a remarkable leap of sensitivity to an unprecedently high level of 133.1 kPa −1 . However, the high sensitivity can only sustain at the pressure up to 30 Pa. It will decrease significantly to 0.05 kPa −1 when the pressure goes above 10 kPa. Therefore, a remaining challenge is how to develop flexible pressure sensors with both high sensitivity and wide operation range. This problem might be solved by using hydrogel with high stretchability and toughness. Suo and co-workers [14] demonstrated a Elastic hydrogels have recently attracted remarkable attention because of their unique mechanical and stimulus-responsive properties. In this work, a novel elastic supramolecular hydrogel for wearable pressure sensors is developed by photocrosslinking polyacrylamide (PAAm) through covalent bonds and hydrogen bonds as well as ionic bonds in the presence of poly(acrylic acid) and Ca 2+ . Gold nanowires (Au NWs) are homogeneously mingled with...